/**
* Testign the speed of executable in Go.
This just creates a large array and sorts it.
* @author gtowell
* created: July 20, 2021
**/
package main

import (
	"bytes"
	"fmt"
	"math/rand"
	"sort"
	"time"
)

//Structs are a lot like classes, but with no inheritance.
//Methods get added separately
type NumAndString struct {
	num int
	str string
}

// name a type that will hold a list of items of the NumAndString type
type NumAndStringSlice []NumAndString
// by having another name, you can associate different sorting
// sort of like static method binding
type StringSlice NumAndStringSlice
// create a variable that will hold a NumAndStringSlice
var aaa NumAndStringSlice

// implementing the function required for sorting 
func (p NumAndStringSlice) Len() int { return len(p) }
func (p NumAndStringSlice) Swap(i, j int) { p[i],p[j] = p[j],p[i] }
func (p NumAndStringSlice) Less(i, j int) bool { return p[i].num < p[j].num }

// implementing the function required for sorting a different way.
func (p StringSlice) Len() int { return len(p) }
func (p StringSlice) Swap(i, j int) { p[i],p[j] = p[j],p[i] }
func (p StringSlice) Less(i, j int) bool { return p[i].str < p[j].str }

/**
* Generate a random string
* @param len -- the length of the string to generate
* @param r1 an initialized random number generator instance
* @return a random string 
*/
func randString(len int, r1 *rand.Rand) string {
	var buf bytes.Buffer
	for i := 0; i < len; i++ {
		buf.WriteString(string('a' + r1.Intn(26)))
	}
	return buf.String()
}

func main() {
	s1 := rand.NewSource(time.Now().UnixNano())
    r1 := rand.New(s1)

	now := time.Now();
	doSort(10000000, r1, false)
	thn := time.Now();
	diff := thn.Sub(now)
	fmt.Println(diff);

}

/**
* Create and fill an array of the desired size, then sort it. 
* report the time required for the two operations
@param num the length of the array to create
@param r1 a random number generator
@param sortByNum how to sort the created array.
**/
func doSort(num int, r1 *rand.Rand, sortByNum bool) { 
	aaa = make(NumAndStringSlice, num)

	for i := 0; i < num; i++ {
		aaa[i] = NumAndString{r1.Intn(num), randString(10,r1)}
	}

	if (sortByNum) {
		sort.Sort(aaa)
	} else {
		sort.Sort(StringSlice(aaa))
	}
	for i:=0; i < 5; i++ {
		fmt.Printf("%v\n", aaa[i])
	}
}